Add copilot crate

Refactor HTTP and github release downloading into util
Lazily download / upgrade the copilot LSP from Zed

Co-authored-by: Max <max@zed.dev>
Co-Authored-By: Antonio <antonio@zed.dev>

crates/util/src/github.rs

@@ -0,0 +1,40 @@
+use crate::http::HttpClient;
+use anyhow::{Context, Result};
+use futures::AsyncReadExt;
+use serde::Deserialize;
+use std::sync::Arc;
+
+#[derive(Deserialize)]
+pub struct GithubRelease {
+    pub name: String,
+    pub assets: Vec<GithubReleaseAsset>,
+}
+
+#[derive(Deserialize)]
+pub struct GithubReleaseAsset {
+    pub name: String,
+    pub browser_download_url: String,
+}
+
+pub async fn latest_github_release(
+    repo_name_with_owner: &str,
+    http: Arc<dyn HttpClient>,
+) -> Result<GithubRelease, anyhow::Error> {
+    let mut response = http
+        .get(
+            &format!("https://api.github.com/repos/{repo_name_with_owner}/releases/latest"),
+            Default::default(),
+            true,
+        )
+        .await
+        .context("error fetching latest release")?;
+    let mut body = Vec::new();
+    response
+        .body_mut()
+        .read_to_end(&mut body)
+        .await
+        .context("error reading latest release")?;
+    let release: GithubRelease =
+        serde_json::from_slice(body.as_slice()).context("error deserializing latest release")?;
+    Ok(release)
+}